1. Field of the Invention
The present invention relates to a method of repairing a disconnected wiring and a multilevel wiring structure and, more particularly, a method of repairing a disconnected wiring to recover a function of the disconnected wiring when the wiring is disconnected, and a multilevel wiring structure.
2. Description of the Prior Art
The development of the flat displays such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), FED (Field Emission Display), etc. has advanced since such flat displays can be increased in size without an increase of their depth rather than the CRT. Actually such flat displays begin to acquire a market. Although their principle and structure employed to display the image are different respectively, such flat displays are common in that wirings are formed around a pixel.
In such display panels, sometimes wirings are disconnected in manufacturing steps. Such disconnection brings about the pixel defect to cause reduction in yield.
Therefore, in the display panel, a spare wiring is provided in a peripheral region of a display region to relieve the defective wiring. In case the disconnection of the wiring is present, the signal can be transmitted to a wiring route, through which the signal cannot be passed because of the disconnection, via the spare wiring. Thus, yield in manufacturing the display panel can be improved.
For example, in the LCD, one end of a drain bus line is connected to a signal driver. As a countermeasure against the disconnection of the drain bus line, such a repair method can be adopted that both end portions of the drain bus line are connected via the spare wiring to relieve the defect of the drain bus line.
FIG. 1A shows a sectional shape in which a drain bus line 1 and a spare wiring 2 of the LCD are formed in sequence via an insulating film 3. As shown in FIG. 1B, both end portions of the drain bus line 1 and both end portions of the spare wiring 2 are intersected with each other in the peripheral region of the display region.
If the disconnection of the drain bus line 1 is caused at a point B shown in FIG. 1B, one-shot irradiation of a laser beam is applied downward to a center of the intersecting region of the drain bus line 1 and the spare wiring 2, as shown in FIG. 1C. Thus, a hole 4 is opened through the drain bus line 1, the spare wiring 2 and the insulating film 3 and at the same time a part of the drain bus line 1 and the spare wiring 2 is melted. Then, the melted portion of the drain bus line 1 and the spare wiring 2 flows through the hole 4, so that the drain bus line 1 and the spare wiring 2 are connected to each other. As a result, conduction of the disconnected drain bus line 1 can be repaired via the spare wiring 2.
In this case, a reference 5 denotes an underlying insulating film in FIGS. 1A and 1C.
According to the above repair technology, unless the drain bus line 1 and the spare wiring 2 can be connected to each other by one-shot irradiation of the laser beam, the laser beam having the same intensity must be irradiated repeatedly. According to such laser beam irradiation, such a possibility becomes high that the intersecting portion of the drain bus line 1 and the spare wiring 2 is destroyed, so that a reliability in wiring defect repair becomes low.
Also, in the conduction portion between the drain bus line 1 and the spare wiring 2, unevenness of an inner surface of the hole 4 is hardly detected by the SEM (Scanning Electron Microscope) investigation. In addition, as shown in FIG. 2, the underlying film is turned up and then remains on the peripheral region of the opening 4. After this, such turned-up film remains in the panel as a foreign matter.
It is an object of the present invention to provide an image displaying device which is capable of improving reliability in wiring defect repair and a method of manufacturing the same.
According to the present invention, upon connecting the main wiring and the spare wiring in their intersecting region, the main wiring and the spare wiring can be connected by two-step method such that the hole is formed in the main wiring and the spare wiring by the laser beam irradiation and then the main wiring and the spare wiring are melted by the laser beam irradiation whose output intensity is changed at that position. Therefore, the main wiring and the spare wiring can be connected without fail in the intersection region, and thus the reliability in repairing the wiring defect can be improved.
In this case, the laser beam is irradiated plural times. However, since the intensity of the laser beam can be changed and adjusted, destruction of the intersection portion of the main wiring and the spare wiring can be prevented beforehand.
Also, in case the laser beam is irradiated onto the intersecting portion of the main wiring and the spare wiring, failure of the laser beam irradiation can be prevented by selecting the edge of the main wiring or the spare wiring as a target. In addition, if the alignment hole is formed previously in the main wiring, the spare wiring, and the protection insulating film in the intersecting portion of the main wiring and the spare wiring, alignment of the laser beam irradiation can be facilitated.
Moreover, since the connected portion of the main wiring and the spare wiring is melted gradually every laser beam irradiation to sublimate if the main wiring or the spare wiring are connected while changing the laser intensity, no rolling-up or burr of the film is caused in the connected portion of the main wiring and the spare wiring. Thus, the foreign matter is hard to remain in the substrate.
A hole formed in the main wiring and the spare wiring by irradiating the laser beam has a rugged or unevenness inner surface.
A shape formed after such laser beam irradiation can be easily decided by the SEM investigation.
As the main wiring, for example, there are the gate bus line, the drain bus line, etc. in the liquid crystal display panel.